Cycloaliphatic sulfides for stabilizing polyolefins

ABSTRACT

CYCLOALKANE BIS(ALKYLSULFIDE) COMPOUNDS OF STRUCTURE   R2,(R1-S-),(R1-S-R&#39;&#39;-)CYCLOHEXANE, AND (R1-S)2-PERHYDRO-   4,7-METHANOINDENE   WHERE R1 IS HIGHER ALKYL, R2 IS H OR LWER ALKYL AND R&#39;&#39; IS LOWER ALKYLENE AND THE USE OF THESE COMPOUNDS IN POLYOLEFINS AS ANTIOXIDANT-SYNERGISTS.

United States Patent 3,772,246 CYCLOALIPHATIC SULFIDES FOR STABILIZING'POLYOLEFIN S Bernard Buchholz, Blue Bell, Pa., assignor to PennwaltCorporation, Philadelphia, Pa.

No Drawing. Original application Aug. 8, 1969, Ser. No. 848,737, nowPatent No. 3,652,680. Divided and this application Jan. 3, 1972, Ser.No. 215,235

Int. Cl. 008i 45/58 US. Cl. 260-4535 R 7 Claims ABSTRACT OF THEDISCLOSURE Cycloalkane bis(alkylsulfide) compounds of structure I IIwhere R is higher alkyl, R: is H or lower alkyl and R is lower alkyleneand the use of these compounds in polyolefins as antioxidant-synergism,

This application is a division of Ser. No. 848,737, filed Aug. 8, 1969,now US. 3,652,680.

It is customary to stabilize polyolefins, particularly polypropylene,against oxidative degradation by incorporating in the polyolefins asmall amount of a phenolic primary antioxidant and a sulfur-containingsecondary antioxidant or synergist. The sulfide synergists now usedalmost exclusively are dilauryl thiodipropionate (DLTDP) or distearylthiodipropionate (DSTDP).

These known thiodipropionate esters DLTDP and DSTDP suffer from the factthat they are gradually leached out of polyolefins by hot water,particularly hot water containing soap or detergents. This gradual lossof stabilizer results in premature deterioration (embrittlement andcracking) of polyolefins when they are used for hot water pipe andtubing applications and as components in automatic laundry and dishwashers, Vaporizers and other hot water equipment.

The compounds of this invention are cycloalkane bis (alkylsulfides)having the general structures I and II shown below where R is higher(Cg-C30) straight-chain alkyl, R is H or lower (C -C straight-chain orbranched alkyl and R is lower (C -C Straight-chain or branched alkylene.These compounds exhibit high activity as antioxidant-synergists.

R1 Rlggqvsm 111038111 They are superior to the thiodipropionates inresistance to hot water leaching and have excellent compatibility withpolyolefins.

The compounds of the invention are readily prepared from commerciallyavailable cyclic' diolefins, H S and Patented Nov. 13, 1973 highermolecular Weight monoolefins as illustrated by the following threeequations:

C H=CH C HzCHaSH CHi z C isHsn +20 nH (oetadecene-l SC iaHrlbeta-(n-octadeeylthio)ethyl-3 (and 4)-(n-octadecyl thlo) cyclohexane (vcyclohexene) (2) CH3 CIHQ (see note) 2,9-bls (n-hexadecy1thio)-p-menthane C lB BH QJ IG M blsl2 (and 3), 5 (and 6)-n-hexadeey1-thloloctahydroi, 7-methanoindene (dlpentene or d-llmonene) (see note)(dlcyclopentadiene) PREPARATIVE PROCEDURE The liquid-phase reaction of4-vinylcyclohexene-1 is carried out with excess H 8 in the presence ofultraviolet light from 15 watt germicidal lamps to produceS-mercaptoethyl-3 (or 4)-mercaptocyclohexane), 979/ 1.25 mm. in highyield.

A solution containing 13 grams (0.073 mol) of vinylcyclohexenedimercaptan and 37 grams (0.146 mol) of octadecene-l in 300 cc. ofmethyl propyl ketone is maintained at about 5 C. while irradiating at47.5 Watts with a Nester/Faust ultraviolet lamp for 5 hours. Filtrationof the precipitated solid gives 25 grams (50%) of the desired product,M.P. 67-69.5. Recrystallization from methyl ethyl ketone gives a softwaxy white crystalline product, M.P. 71-72 C.

Analysis.-Calculated for C H S (percent): C, 77.57; H, 13.02; S, 9.41.Found (percent): C, 76.90; H, 12.95; S, 9.48.

The preferred compounds are rivatives III CHzCHzSR III M.P., C.Beta-(n-dodecylthio)ethyl-3 (and 4)-(n-dodecylthio)cyclohexane 49.5-50.5Beta-(n-hexadecylthio)ethy1-3 (and 4 -(n-hexcylthio)cyclohexane 63-64Beta-(n-octadecylthio)ethyl-3 (and 4)-(n-octadecylthio)cyclohexane 71-72Beta-(n-eicosylthio)ethyl-3 (and 4)-(n-eicosylthio cyclohexane Beta-(n-C-C alkylthio)ethyl-3 (and 4)-(n- Cgz-Cgg alkylthio)cyclohexane 72.5-74.5

2,9-bis (n-hexadecylthio -p-menthane 5 1-562,9-bis(n-octadecylthio)-p-menthane 62-63 Bis[2 (and 3), 5 (and6)-n-hexadecylthio)octahydro-4,7-methanoindene 52-525 The compounds ofthe invention have low toxicity which is of value when used inpolyolefin bottles and film for packaging materials. Thus, for example,beta-(n-octadecylthio)ethyl-3 (and 4)-(n octadecylthi0)cyclohexane wasfound to be non-toxic when administered orally to mice at doses as highas 10 g./ kg.

In using the compounds of the invention a synergizing amount will beemployed together with the phenolic antioxidant. Usually from about 0.02to 0.5% by Weight of the formulated polyolefin will be antioxidant andfrom about 0.02 to 1.5% weight will be synergist. Preferably the amountof synergist used will be 0.05-0.5%.

EXPERIMENTAL The compounds were evaluated as antioxidant-synergists inpolypropylene. The polypropylene test samples were prepared by dryblending 0.1% by Weight of a commercial phenolic primary antioxidantsuch as Ionox 320 (a) (Shell), Irganox 1010 (b) (Geigy) or Topanol CA(c) (ICI) and 0.1% or 0.25% by weight of the synergist into unstabilizedpolypropylene (Hercules Profax 6501 flake), extruding into A inch rods,pelletizing, and hot pressing at 200-225 C. into 10 mil thick sheets.Unless otherwise specified all alkyl groups corresponding to R arestraight-chain alkyl.

The synergists were compared with control samples containing DSTDP instandard oven aging tests, i.e., the average hours to embrittlement of10 mil samples in a 140 C. air-circulating oven were determined. Theresults are tabulated below. The data show that the subject thevinylcyclohexene decompounds are highly active synergists, comparable toDSTDPr'Fhe-data also show (Test'Nosr'7 and 8) that simple higher alkylsulfides such as (n-C H S and (11-C13H3'7)2S, contrary to thedisclosures in British Pat. 953,447 (1964) and Italian Pat. 662,492(1964), are not active synergists.

(a) Ionox 330 (b) Irganox 1010 t-C 4H t-C 411 11101130 0 C CHITC (c)Topanol CA A 3:1 condensate of 3-methyl-6-t-butylphenol andcrotonaldehyde.

TEST N0. 1

Primary antioxidant: 0.1% Irganox 1010 CHzCHz S R1 Synerglst: 0.15%

Average hours TEST N0. 3 TEST 7 Stabilizers: 0.17 Topanol CA Primaryantioxidant 0.1% Irganox 1010 0. synergist OHZCH S Average. hoursstabilization Percent hours Synergist at 140 C. of DSTDP Synergist:0.25% (C1eHaa)2 64 8 114113028 104 13 zCH2SC1aHa7 604 77 5 P1 Averagehours stabilization Percent hours 1 at 140 C. of DSTDP I1-C12H2 1, 34780 11-01013; 1, 415 87 S 018E DSTDP (Control) 1, 688 15 DSTDP 00111101829 TEST N O. 8 Stabilizers: 0.1% Topanol CA 0.25% synergist Averagehours TEST 4 stabilization Percent hours Stabilizers: 0.1% Irganox 1010Synerglst at 140 C. of DSTD 025% Synerglst (C1BHB3)2S 96 11 g l oi lq gpP t h (C1sHa7)2S 181 20 s a ma ion ereen ours Synergist at 140 0. 01DS'IDP CHZCHZSCWH" 731 CHzCHzS CH CH COOC12Hz5 1,149 61 SCm aa s CH2CH2CO 0 Cnflfi C 2CH2SC111H31 712 78 (A liquid product) CHzCHzS (3121125 1,611 86 2CH2SC2r2a -51 840 92 DSTDP (Control) 1, 872

SO22-zaH4a-s7 (See note) TEST 5 DSTDP (Control) 9 Primary antioxidant:0.1% Ionox 330 NOTE.-Prepared as described above by 1 :2 molar reactionof M3 (and Synergist o. 25% 311.011, s R1 94)-mercaptoeyelohexyl]ethanethiol with a commercially available Caz-2anormal alpha olefins mixture.

TEST N O- 9 Stabilizers: 0.1% Irganox 1010 0.25% synergist P 1 1 lf P to ypropy ours ercen S R1 ene stabilihours sample zation of Average hours0- Synergist (0.25%) at 140 C. DSTDP stabilization Percent hours 1 CH CHS-b h dC H 727 33 R at 140 0. of DSTDP 2 mm e I1-C1aHa1 083 81 ll-CZDHfl1, 234 93 DSTDP (C0ntr01)- 1, 341

S-branched C1sHz7 I HgCHzS-D.-C1ZH25 1, 611 I 86 TEST NO. 6

Stabilizers: 0.1% Topanol CA 0.25% synergist Average hours S-n-C Hstabilization Percent hours n Synergist at 140 C. of DSIDP 3 3 1,566 71cllizoHzs 01111133 507 100 S-l1-C1u 3fl CH S 0101111 C 3 cflaS-n-CwHaa 4DLTDP 1,603 73 DSTDP 507 7 5 DSTDP (Control) 2,193

As can be seen, 2,9-bis(n-hexadecylthio)-p-menthane (sample 3) is aboutas effective as the commercial DLTDP. Also evident is that branchedhigher alkyl groups (sample 1) are relatively ineffective compared tostraightchain alkyls.

TEST NO. 10

In oven aging tests at 140 C. as above, polypropylene containing 0.1%Irganox 1010 and 0.1% bis[2 (and 3), 5 (and6)-n-hexadecylthio]octahydro-4,7-methanoindene showed a stabilizationwithout embrittlement about equivalent to the control of 0.1% Irganox1010 and 0.1% DSTDP.

The compounds of this invention are particularly advantageous in thatthey are resistant to hot water leaching. This property is demonstratedby the following method:

Samples of polypropylene containing 0.1% Irganox 1010 plus 3.0%synergist were extruded and chopped to fine particle size. The samples(100 g.) were placed in an autoclave with 500 cc. distilled H 0 andmaintained at 100 C. for 48 hours with shaking. The sulfur content ofthe water from each sample was determined analytically and the percentsynergist that leached from the polypropylene sample was calculated fromthe analyses. The results follow.

Synergist: Wt. percent leached DLTDP 0.75 DSTDP 0.71Beta-(n-octadecylthio)ethyl-3 (and 4)-(n-octadecylthio)cyclohexane 0.35

The conventional primary phenolic antioxidants which will be used withthe olefinic polymers will include both monohydric and polyhydricphenols and include bis-phenols, tris-phenols and tetrakis-phenols.

Monohydric phenols useful in the invention include those disclosed inUS. 2,581,907 and include the following:

2,4-dimethyl-6-t-butylphenol 2,4-dimethyl-6-( alpha, alpha, gamma,gamma-tetramethylbutyl) phenol 2,6-di-t-butyl-4-methylphenol2-methyl-4,6-t-butylphenol 2,6-di-t-butyl-4-sec-butylphenol2,4,6-tri-t-butylphenol 2,4,6-triethylphenol 2,4,6-tri-n-propylphenol2,4,6-triisopropylphenol 2,6-di-t-octyl-4-propylphenol2,6-di-t-butyl-4-ethylphenol 2,4-dicyclohexyl-6-methylphenol2-isopropyl-4-methyl-6-t-butylphenol 2,4-dimethyl-6-t-amylphenol2,4-di-t-amyl-6-methylphenol 2,6-di-t-butyl-4-isopropylphenol2,6-di-t-amyl-4-methylphenol 2,6-di-t-amyl-4-isopropylphenol2,4-diisopropyl-6-t-butylphenol, and 2,4-diisopropyl-6-sec-hexylphenolThe preferred compounds of this class are those which have secondary ortertiary alkyl groups at the 2- and 6- positions and a normal alkylgroup at the 4-position, a representative of this class being2,6-di-t-butyl-p-cresol. More preferably, the normal alkyl group in the4-position is one containing from about 1 to 20 carbon atoms while thesecondary or tertiary alkyl groups in the 2- and 6-positions eachcontain from about 3 to 20 carbon atoms. Any of the dialkylphenols aresuitable; particularly preferred is the 2,6-di-t-butylphenol. Thebisphenols are characterized by the general formula OH OH wherein R isan alkylidene radical of 1 to 5 carbon atoms, or is an ether orthioether group, and wherein R is an alkyl group of 1 to 12 carbon atomsand n is an integer from 1 to 3. When more than one R' substituent ispresent on a phenyl group, each R can be the same or different.

Exemplary of these alkylidene-bis(alkylphenols) that may be used are2,2-methylene-bis(S-isopropylphenol), 2,2-methylene-bis(4-methyl-6-isopropylphenol 2,2'-methylene-bis 4-methyl-6-t-butylphenol)2,2-methylene-bis(4-t-butyl-6-methylphenol),2,2'-methylene-bis(4,6-di-t-butylpheno1),2,2'-methylene-bis(4-nonylphenol),4,4-methylene-bis(2,6-di-t-butylphenol), 2,2'-isopropylidene-bis(Smethylphenol), 4,4-methylene-bis 2-methyl-6-t-butylphenol2,2'-ethylidene-bis(4-methyl-6-t-butylphenol),2,2-ethylidene-bis(4,6-di-t-butylphenol), 2,2'-ethylidene-bis(4-octylphenol) 2,2-ethylidene-bis (4-nonylphenol)2,2'-isopropylidene-bis(4-methyl-6-isopropylphenol),2,2-isopropylidene-bis(4-isopropylphenol), 2,2-isopropylidene-bis(4-isopropyl-6-methylphenol)2,2'-isopropylidene-bis(4-methyl-6-t-butylphenol),2,2-isopropylidene-bis(4-octylphenol),2,2'-isopropylidene-bis(4-nonylphenol),2,2-isopropylidene-bis(4-decylphenol),2,2-isobutylidene-bis(4-methyl-6-t-butylphenol), 2,2-isobutylidene-bis(4-nonylphenol 4,4'-butylidene-bis( 3-methyl-6-t-butylphenol) 1,1-thiobis- (2-naphthol) Bis(3,5-di-tert.-butyl-4-hydroxybenzyl) ether,2,2'-thiobis- (4-methyl-6-tert.-butylphenol) and 4,4'-thiobis-(5-methyl-2-tert.-butylphenol) Of the tris-phenols useful1,3,5-trimethyl-2,4,6-tris(3,5- di-tertiary-butyl-4-hydroxybenzyl)benzene and 1,3,5-trimethyl-2,4,6-tris(3,5 di isopropyl 4 hydroxybenzyl)benzene and the like are typical.

Tetrakis-phenols useful are exemplified by compounds such as those ofstructure JI'hCHIC o 0 011 -0 J4 where R is lower alkyl. Preferredwithin this group is the compound where R is t-butyl.

The particular polyolefins which are to be treated in accord with thisinvention are any of the numerous polyolefin polymers. These willinclude the hydrocarbon polymers such as polyethylene, both conventionaland the 'more recent higher density materials, polypropylenepolybutene-l, poly-3-methylbutene-l, poly-4-methylpentene-1, poly-4,4-dimethylpentene-1, polydodecene-l, and poly-3- methylpentene-l,polybutadiene, polystyrene, etc. It will be understood, of course, thatpolymers derived from mixtures of appropriate olefins such asstyrene-butadiene, acrylonitrile-butadiene-styrene, orethylene-propylene-dicyclopentadiene may also be treated in accordancewith the invention.

I claim:

1. The polyolefinic composition containing a phenolic antioxidant and asynergizing amount of a compound selected from the group consisting ofwhere R is straight-chain alkyl group of from about 8 to about 30 carbonatoms, R is hydrogen, methyl or ethyl and R is an alkylene group of fromtwo to about four carbon atoms.

2. The composition as in claim 1 where the polyolefin is polyethylene.

3. The composition as in claim 1 where the polyolefin is polypropylene.

4. The composition as in claim 1 where the polyolefin is polypropyleneand the synergist is beta-(n-octadecylthio)ethyl-3 (and4)-(n-octadecylthio)cyclohexane.

5. The composition as in claim 1 where the polyolefin is polypropyleneand the synergist is 2,9-bis(n-hexadecylthio)-p-menthane.

6. The composition as in claim 1 where the polyolefin is polypropyleneand the synergist is 2,9-bis (n-octadecylthio)-p-mer1thane.

7 The composition as in claim 1 where the polyolefin is polypropyleneand the synergist is bis[2 (and 3), 5 (and6)-n-hexadecy1thio]octahydro-4,7-methanoindene.

References Cited UNITED STATES PATENTS Buchholz et a1 26047.75 Braus eta1 26047.95 Baldwin et a1 26045.7 Braus et al 260--45.7 Hechenbleikner26045.7 May et a1 26045.7 Fanning et al 26045.7 Schooten et a1. 26045.85Homberg et al 26045.85

' DONALD E. CZAJA, Primary Examiner 15 V. P. HOKE, Assistant ExaminerU.S. Cl. X.R.

